The complete evolution of holmium-laser-pulse-induced cavitation bubble movements and acoustic transients underwater are investigated experimentally. The laser was single fiber-guided and had a 300 mJ pulse energy and 300 μs pulse duration (full width at half-maximum). In our experiments, more than four oscillations and four acoustic transients were demonstrated. 272 μs after laser onset, the cavitation bubbles reached their maximum transverse and longitudinal lengths of 2046 and 1914 μm, respectively. The maximum transverse and longitudinal bubble wall velocities were 28.9 and 39.2 m/s at 560 and 528 μs after laser onset, respectively. This investigation will be helpful to make good use of cavitation effect in medical applications of holmium laser pulses.
To clarify the role of a natural or artificial liquid environment in the free-running infrared pulsed laser ablation of hard biological tissues,two-and three-dimensional morphologies of laser-induced craters must be quantitatively measured to distinguish ablation differences in air and in water.Full-field optical coherence microscopy is introduced,which has non-contact,non-destructive,non-preprocessing and higher-resolution advantages.Experimental results indicate that the ablation performances in air and in water are comparable for few laser pulses,but the ablation difference becomes obvious for more laser pulses.Optical coherence microscopy is more feasible than conventional means for the morphological measurement of craters.
